Process for introducing zinc micronutrients into liquid fertilizers

ABSTRACT

Zinc particulate compositions precoated with aliphatic amines, salts of such amines or mixtures thereof, when added to phosphate-containing liquid fertilizers, avoid lumping and caking which otherwise occurs when uncoated zinc compositions are added to such liquid fertilizers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of Ser. No. 321,924, filedJan. 8, 1973, now U.S. Pat. No. 3,796,559 which is a continuationapplication of Ser. No. 129,109, filed Mar. 29, 1971, now abandoned,which in turn is a continuation-in-part application of Ser. No. 867,905,filed Oct. 20, 1969, now abandoned.

BACKGROUND OF THE INVENTION

Commercially available liquid fertilizers include the primary plantnutrients, nitrogen, phosphorus and potassium dissolved or suspended inwater. Besides these primary nutrients, the soil also requires smalleramounts of micronutrients such as zinc, manganese, iron and copper.Particulate zinc compositions are difficult to blend with liquidfertilizers, because these zinc compositions agglomerate and form lumpsand cakes which frequently adhere to the mixing vessel. With vigorousagitation the lumps can be broken apart and dispersed or dissolved inthe fertilizer. This, however, is both an expensive and time consumingoperation that desirably should be eliminated.

SUMMARY OF THE INVENTION

I have found that particulate zinc compositions precoated with aliphaticamines, or mixtures thereof can be added to and dispersed in liquidphosphate-containing fertilizer without lumping or caking. Thus vigorousand excessive agitation is avoided with attendant reduction in equipmentwear and time required to make the fertilizer. Adding the coatingmaterial to the liquid fertilizer instead of precoating the zinccomposition does little to reduce lumping. I have also found thatmaterials such as stearic acid, paraffin wax and motor oil have noappreciable effect in reducing lumping and caking.

LIQUID FERTILIZER

Most liquid fertilizer contains at least about 30 weight percent plantnutrient such as compounds of nitrogen, phosphorus and potassium. Thephosphorus and potassium concentrations are conventionally expressed asoxides. The proportions of nitrogen, phosphorus and potassium vary, asfor example, 1:1:1, 1:2:1, 1:3:1, 1:3:0, 2:3:1, 4:3:1, etc.

Sources of nitrogen suitable for use in the preparation of the basefertilizer include ammonia, urea, ammonium nitrate, ammonium sulfate andmixtures thereof. Ammonia may be used in either aqueous or anhydrousform. Urea, ammonium nitrate and ammonium sulfate may be used in solidform or as an aqueous slurry or solution.

Phosphatic compounds suitable for use in preparing fertilizers includeconcentrated aqueous phosphoric acid solutions, monoammonium phosphates,diammonium phosphates, or mixtures thereof. Ammonium phosphates can beused in either solid or aqueous form. Superphosphoric acid prepared byeither the "furnace process" or "wet process" is a preferred source.

Suitable sources of potassium are potassium salts such as potassiumchloride, potassium sulfate, potassium nitrate, and the like. Potassiumchloride is the preferred source.

Liquid fertilizer may also include dispersed material. For example, clayis sometime added to the fertilizer to suspend particles of potassiumchloride or the like. In addition to the zinc, other micronutrients suchas iron, magnesium, manganese or other metals may be included. Sometimesherbicides and pesticides are also added to the fertilizer.

PARTICULATE ZINC COMPOSITIONS

Suitable sources of zinc include zinc sulfate (preferably themonohydrate), zinc oxide, zinc carbonate, or free metallic zincparticles. Generally, these zinc compositions are powders havingparticles ranging in size from about 25 to about 1000 microns. In mostinstances they are used in liquid fertilizers in concentrations rangingfrom about 0.05 to about 1.0 weight percent zinc, based on totalfertilizer weight. This is normally considered an agronomically activeamount, but this amount can vary somewhat depending upon the soilconditions.

COATING MATERIALS

The materials used to pre-coat the solid particulate zinc materials foruse in the present invention are aliphatic monoamines and diamines,having from 6 to 40 carbon atoms in the aliphatic moiety, selected fromthe group consisting of (a) primary-, secondary-, and tertiary-aliphaticamines, (b) alpha, omega-diaminoalkanes, (c) N-aliphatic 1,3 propylenediamines, (d) salts of said amines and (e) mixtures thereof. The group(a) amines are represented by the formula ##EQU1## wherein R is anunsubstituted straight or branched chain aliphatic group, and R₁ and R₂are hydrogen or R, and the total number of carbon atoms in the formulais from 6 to 40. The group (b) diamines are represented by the formulaH₂ N--(CH₂)_(x) --NH₂ wherein x is from 6 to 40. The group (c) diaminesare represented by the formula R--NH(CH₂)₃ NH₂ wherein R is an aliphaticgroup as defined above, and the total number of carbon atoms in theformula are 6 to 40. Examples of suitable aliphatic amines arelaurylamine, oleylamine, stearylamine, n-tetradecylamine,n-tetracontylamine, n-hexylamine, N, N-dimethyl dodecylamine,2-ethylhexylamine, tri-n-octylamine, di-n-nonylamine,1,8,-diaminooctane, and 1,11-diaminoundecane. Armour Industrial ChemicalCompany also sells a number of suitable aliphatic amines such as DuomeenO (oleic 1,3-propylenediamine), Duomeen S (soya 1,3-propylenediamine),Armeen 18D (n-octadecylamine), and Armoflow 610.

I have also found that the salts of the aliphatic amines are alsosuitable coating materials, and have tested oleylamine acetate andoleylamine hydrochloride on zinc sulfate (monohydrate). I have foundsuch salts are as effective as the oleylamine itself. The oleylamineacetate and oleylamine hydrochloride were applied to the zinc sulfate ina solution of methylene chloride and ethyl ether.

If the amine has the general formula R₃ N, where R may represent thesame or different aliphatic groups or aliphatic and hydrogen groups, thefollowing salts are suitable:

1. (R₃ NH)⁺ X⁻ (monovalent anion): X⁻ = NO₃ ⁻ (nitrate), Cl⁻ (Chloride),Br⁻ (bromide), H₂ BO₃ ⁻ (borate), CH₃ COO⁻ (acetate), CH₃ (CH₂)₄ COO⁻(hexanoate).

2. (R₃ NH)₂ ^(+X) ⁼ (divalent anion): X⁼ = SO₄ ⁼ (sulfate), HPO₄ ⁼(dibasic phosphate), etc.

3. (R₃ NH)₃ ⁺ X (trivalent anion): X = PO₄ (tribasic phosphate), etc.

4. Amine salts of polymeric acids, such as polyacrylic acid or poorlycharacterized acids, like lignosulfonic acids.

5. Complexes of zinc salts such as (R₃ N)_(y) Zn⁺ ^(+X) ⁼ or (R₃ N)_(y)Zn⁺ ^(+X) ₂ ⁻, etc., where y = 1 to 4.

Converting the amines to salts will in general change their solubilitycharacteristics, and new solvent systems might have to be employed fortheir use in coating the zinc salts.

Conventional coating techniques can be employed in precoating zincparticulate compositions. For example, coating materials may bedissolved in a suitable solvent, with the solid particulate zincmaterials then being mixed with this solution. Or, the coating materialand the particulate composition may be mixed together directly. If thecoating material is first dissolved in the solvent, the solvent shouldnot react with the particulate composition. Suitable solvents are, forexample, heptane, xylene, petroleum distillates, ethyl ether, dibutylether, trichloroethylene, and methylene chloride.

The amount of coating material is not critical. As little as 0.005weight percent coating material, based on the weight of particulatecomposition, has been effective. Normally, the amount of coatingmaterial ranges from about 0.05 to about 1.50 weight percent, based onweight of particulate composition. With solid amines, the addition ofexcessive amounts (about 2 weight percent) leaves an obvious residue inthe fertilizer. With some liquid amines, using more than about 1 weightpercent tends to make the zinc particulate composition stick together.However, different coating materials behave differently, and the amountsemployed will therefore vary.

ADDING METALLIC ZINC PARTICLES TO LIQUID FERTILIZERS

While investigating ways to introduce zinc micronutrients into baseliquid fertilizer, I found that metallic zinc particles can be addeddirectly to the base fertilizer. When this is done some caking occursand hydrogen gas is liberated. Since hydrogen gas and air form anexplosive mixture, it is necessary to suppress the formation of hydrogengas. This can be achieved if the fertilizer includes an oxidizing agentin an amount sufficient to react with the expected quantity of hydrogenordinarily produced.

Nitrate salts, nitrite salts, hydroxylamine or nitroparaffins areexamples of effective oxidizing agents for suppressing the formation ofhydrogen. The nitrate and nitrite salts and hydroxylamine are reduced toammonia which dissolves in the fertilizer. The nitroparaffins, however,are reduced to alkyl amines. Thus if the zinc particles are firstprecoated with nitroparaffins containing more than 6 carbon atoms, it ispossible to suppress hydrogen formation and simultaneously preventlumping. Nitroparaffins such as nitroethane, 2-nitrobutane, etc., up toabout nitrohexane, could be used as hydrogen acceptors whilenitroparaffins from about 6 carbon atoms up to about 40 carbon atomscould be used in smaller amounts as coating agents.

Alternately, free metal particles of zinc can be precoated withaliphatic amines so that caking is avoided. Precoating, however, doesnot seem to increase the rate at which the metal is dissolved in thefertilizer, but adding ammonia to the mixture does increase thisdissolving rate. Preferred zinc particle size ranges between about 50and about 100 microns. Such precoated zinc particles are dissolved inthe fertilizer which includes sufficient oxidizing agent to suppress theformation of hydrogen gas.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1

Forty grams of zinc sulfate monohydrate and 0.5 grams of Armeen 18D weremixed together and warmed at 80°C for about 1 hour in an Erlenmeyerflask. The contents of the flask were allowed to cool and then mixedwith 500 grams of commercial 7-24-3 liquid fertilizer. The coated zincsulfate tended to float on the surface of the fertilizer. Very littlelumping was observed. The zinc sulfate was completely dissolved in 15minutes as opposed to 1 hour for uncoated zinc sulfate. The uncoatedmaterial also formed lumps and required a great deal of agitation todissolve.

EXAMPLE 2

This example was substantially the same as example 1 exceptdi-n-nonylamine was substituted for the Armeen 18D.

EXAMPLE 3

This example was substantially the same as example 1 except 0.4 grams oftetradecylamine was substituted for the Armeen 18D.

EXAMPLE 4

This example was substantially the same as example 1 except n-hexylaminewas substituted for the Armeen 18D.

EXAMPLE 5

This example was substantially the same as example 1 except 1,8diaminooctane was substituted for the Armeen 18D.

EXAMPLE 6

This example was substantially the same as example 1 except 1,11diaminoundecane was substituted for the Armeen 18D.

EXAMPLE 7

This example was substantially the same as example 1 excepttrioctylamine was substituted for the Armeen 18D.

EXAMPLE 8

This example was substantially the same as example 1 except Duomeen Owas substituted for the Armeen 18D. The Duomeen O was very effective.

EXAMPLE 9

With gentle mixing, 50 grams of zinc oxide and 0.2 grams of the Armeen18D were blended together and heated at about 120°C for about 2 minutes.Six grams of this precoated zinc oxide was then dissolved in 300 gramsof commercially available 7-24-3 liquid fertilizer. The precoated zincoxide floated on the liquid fertilizer before going into the solution,which took about 10 minutes. Precoated zinc oxide showed no tendency tolump or cake.

EXAMPLE 10

This example was substantially the same as example 1 except zinccarbonate was substituted for zinc sulfate. Zinc carbonate effervescesin the liquid fertilizer, and carbon dioxide evolves. The evolution ofthe carbon dioxide impairs caking in the early stages of mixing;however, precoated zinc carbonate dissolves faster than uncoated zinccarbonate, and caking in the latter stages of mixing is avoided.

EXAMPLE 11

Five hundred grams of 3-10-8 liquid fertilizer, 30 milliliters of 15molar ammonium hydroxide, and 10 milliliters of 28-0-0 ammonium nitrateand urea solution (38.8 weight percent ammonium nitrate) were mixedtogether to give a solution of pH 8.7. With stirring, 5.0 grams of zincdust (particles ranging in size from about 50 to about 100 microns) wasadded to the solution. The zinc particles dissolved in about one andone-half minutes. No hydrogen evolved, but a small cake formed and stuckto the bottom of the reaction vessel.

EXAMPLE 12

This example is substantially the same as example 11 except zinc powderwas first precoated with about 0.2 weight percent oleylamine. Thisavoided caking.

I claim:
 1. In the preparation of zinc-containing liquidphosphate-containing fertilizers which comprises incorporating byadmixing and dissolving particulate solid zinc-containing material ofthe group consisting of zinc sulfate, zinc oxide, zinc carbonate andmetallic zinc in a liquid phosphate-containing fertilizer, theimprovement comprising incorporating said zinc material that has beencoated with from about 0.005 to about 2 wt. percent of a coatingmaterial having from 6 to 40 carbon atoms selected from the groupconsisting of (a) primary-, secondary-, and tertiary-aliphatic amines,(b) alpha, omega-diaminoalkanes, (c) N-aliphatic 1,3-propylenediamines,(d) salts of said amines and (e) mixtures thereof.
 2. The process ofclaim 1 wherein said coating material is selected from the groupconsisting of n-hexylamine, tetradecylamine, n-octadecylamine,oleylamine, di(n-nonyl) amine, trioctylamine, 1,8-diaminooctane,1,11-diaminoundecane and N-oleic 1,3-propylenadiamine.
 3. The process ofclaim 1 wherein said zinc-containing material is zinc sulfate.
 4. Theprocess of claim 3 wherein said coating material is selected from thegroup consisting of n-hexylamine, tetradecylamine, n-octadecylamine,di-(n-nonyl) amine, trioctylamine, 1,8-diaminooctane,1,11-diaminoundecane and trioctylamine.
 5. The process of claim 1wherein said zinc-containing material is zinc oxide, and said coatingmaterial is n-octadecylamine.
 6. The process of claim 1 wherein saidzinc-containing material is zinc carbonate, and said coating material isn-octadecylamine.
 7. The process of claim 1 wherein said zinc-containingmaterial is metallic zinc, and said coating material is oleylamine.